Erectile dysfunction (ED) refers to the inability to persistently reach and/or maintain a full erection for satisfactory sexual life. According to statistics, about 150 million men worldwide have different degrees of ED symptoms, and it is predicted that the number of such patients will double by 2025. PDE5 (5-type phosphodiesterase) inhibitors are the most mature ED therapeutic drugs currently studied. Five of such drugs approved for marketing today are sildenafil, tadanafil, vardenafil, udenafil and mirodenafil. It has been reported in the literature that such compounds have strong selective inhibition on phosphodiesterase, which has attracted wide attention and become a new research hotspot. Related studies have carried out extensive structural modifications to such compounds in order to improve their activity and selectivity to phosphodiesterase 5.
A series of sildenafil analogues synthesized have been reported in the literature, among which, Da Yuanfeng et al. (Study on Synthesis of Sildenafil Analogue, China Contemporary Medicine, Vol. 21, No. 5, February 2014) synthesized a sildenafil analogue (WG001), the chemical name of which is 5-[2-ethoxy-5-(4-methylpiperazin-1-ylthiocarbonyl)phenyl]-1-methyl-3-n-propyl-1,6-dihydro-pyrazolo[4,3-d]pyrimidin-7-thione, and the structural formula is as follows:

The Chinese patent “Synthesis Method of Sildenafil Analogue” (CN104650093A) improves the above synthesis method of the sildenafil analogue, and details the preparation method of the sildenafil analogue.
The crystal form is a different solid state formed by arranging compound molecules or atoms differently in a lattice space. Different crystal forms of the same drug may have significant differences in stability, bioavailability and the like, thereby affecting the efficacy of the drug. Therefore, the study on the crystal form of a drug is an important part of the research on the material basis of drugs, but no crystal form of 5-[2-ethoxy-5-(4-methylpiperazin-1-ylthiocarbonyl)phenyl]-1-methyl-3-n-propyl-1,6-dihydro-pyrazolo[4,3-d]pyrimidin-7-thione methanesulfonate drugs has been reported at present. Moreover, the sildenafil analogue has some drawbacks in drug metabolism, and the bioavailability needs to be further improved.